<!DOCTYPE html>
<html>
<head>
	<title></title>
</head>
<body>
		<div>Html + Css +JavaScript</div>

</body>
</html>
<style type="text/css"> 
	div{
	color:red;
	font-size:50px;
	font-style: italic;
	}
</style>
<script type="text/javascript">
	let div = document.querySelector('div');
	let timer = null;
	let flag = true;
	div.onmouseover = function() {
		timer=setInterval(function(){
			if(flag){
				flag=false;
				div.style.color="blue";
				div.style.fontStyle="normal"}else{
					flag=true;
					div.style.color="red";
					div.style.fontStyle="italic";
				
			}
		},500)
	}
	div.onmouseout=function(){
		clearInterval(timer);
	}
</script>